Leading the study was musicologist Alisun Pawley, previously a graduate student at the University of York, who spent 30 nights covertly observing crowds singing at pubs and nightclubs in five English cities. Whenever a round of song broke out, Pawley noted the fraction of people participating and the crowd’s size and average age. She witnessed over 1,000 episodes in total. A singer herself, she admitted to sometimes joining in.

Pawley and University of London music psychologist Daniel Müllensiefen later modeled the influence of both musical and contextual variables, hoping to discern some trends in singalong behavior.

A prominent feature among the songs was a male vocalist with a loud, clear high-chest voice, without many vocal embellishments. Pawley suggested that singing along to these songs promotes a kind of “neotribal bonding” among participants. As for why female vocalists’ songs weren’t popular, Pawley speculated that, whereas women will happily sing along to men, men may feel that voicing a woman’s words threatens their masculinity.

More important than a song’s musical characteristics, though, was the context in which it was played. The most favorable conditions for sing-alongs were bigger venues with younger crowds, especially on weekends. Not surprisingly, these are all conditions associated with an atmosphere of revelry. Younger people are also more likely to be single, and “when you’re single there’s an added goal” to singing, Pawley said. Most of the songs had been chart-toppers at some point, so familiarity was likely also a factor.

Some of the popular songs are specific to British audiences. “It’s a completely different market from America,” said music industry blogger Bob Lefsetz. “It’s a different bar culture there to begin with.” But while the favorite American sing-along songs my differ from the British, Pawley thinks they’d probably have similar musical qualities to those she found.

“From an evolutionary perspective, we’ve been singing since we were monkeys,” said Pawley. “I think it just makes us feel connected.”